Cold die casting malleable metals



g- 1, 1967 1.. J. RATTE ETAL 3,333,455

cow DIE CASTING MALLEABLE METALS Filed Nov. 1, 1 63 v 5 Sheets-Sheet 1s1 V r 52 y Hj 57 56 o INVENTORS ROBERT W. RAT TE LEON J. RATTE 1, 1967L. J. RATTE ETAL 3,333,455

com um CASTING MALLEABLE METALS Filed Nov. 1 196s s Sheets-Sheet 2INVENTORS ROBERT W. RATTE LEON J. RATTE I g- 1967 1.. J. RATTE ETAL.3,333,455.

COLD DIE CASTING MALLEABLE METALS Filed Nov. 1, 1963 5 Sheets-Sheet 3i'ihillli 22 INVENTORS ERT W. RA'ITTE N J. RATTE Aug. 1, 1967 L. J.RATTE ETAL 5 COLD DIE CASTING MALLEABLE METALS Filed Nov. 1. 1963 5Shets-Sheet 4 FlG.lO

INVENTORS LEON J. RATTE Aug. 1, 1967 L. J. RATTE ETAL COLD DIE CASTINGMALLEABLE METALS 5 Sheets-Sheet 5 Filed Nov.

FIG. l2

FIG.

INVENTORS ROBERT W. RATTE BY LEON J. RATTE United States Patent 3 333455 COLD DIE CASTING MALLEABLE METALS Leon J. Ratte, 1686 Whitaker St.,and Robert W. Ratte, 212 Krech St., both of White Bear Lake, Minn. 55110Filed Nov. 1, 1963, Ser. No. 320,715 4 Claims. (Cl. 72-354) Thisinvention is directed toward die casting metals and specifically it isdirected toward a method for cold die casting malleable metals, theproduct resulting from said method and apparatus constructed to producearticles in accordance with said method.

Certain advantages are to be gained by cold die casting metals accordingto this invention. One advantage is that articles can be produced fasterthan by more conventional processes of molding with hot molten metal. Asingle die casting machine constructed according to the teachings of theinvention can produce the same quantity of articles in a given period oftime that is normally produced by a plurality of hot molding machines. Afurther advantage is that no metal flashing occurs on the articlesformed by the cold die casting process of this invention so there is nonecessity for trimming the finished product. Furthermore, articles ofprecise dimensions may be formed by the cold die casting process of thisinven tion by controlling to a precise degree the feeding of thematerial being cast. The latter results in a further advantage since theamount of material for forming the finished product can be accuratelypredetermined and fed in as required so that no waste results. Otheradvantages are achieved by not subjecting the material to a heating andcooling cycle so there is no shrinkage of the finished product, noadverse change in the characteristics of the material due to heating andcooling, and the product may be handled immediately after fabrication.

These and other features and advantages will be evident from thedetailed description of the process of this invention and an embodimentof an apparatus for producing articles in accordance with said processas contained in the following specification with reference to theaccompanying drawings in which:

FIGS. 19 schematically illustrate the process steps of the invention;

FIG. 10.is a perspective view of an embodiment of an apparatus forperforming the process;

FIG. 11 is a partially broken front elevation view of the apparatusshown in FIG. W

FIG. 12 is a horizontal sectional view of the apparatus;

FIG. 13 is a View along section line A-A of FIG. 12;

FIG. 14 is a view along section line BB of FIG. 12;

FIG. 15 is a view along section line CC of FIG. 12;

FIG. 16 is an enlarged view of the encircled area D of FIG. 12;

FIG. 17 is an enlarged view taken along section line E-E of FIG. 11;

FIGS. 18 and 19 are two views of an article produced by an apparatusconstructed according to the teachings of this invention.

The process requires that a volume of malleable metal be injected into aclosed cavity of a mold with continuous compression force applied, suchthat when the metal strikes the cavity-defining wall surface of the moldit shapes in a homogeneous mass to the contour of the cavity. The volumeof material injected is equal to the volume of metal in the desiredformed article so it can be readily predetermined. No pre-treatment,such as heating to soften the metal, is required. Preferably, a lengthof a cold cylinder of the malleable metal, having a uniformcross-section along its length, is injected lengthwise into the cavityto impact the cavity wall with the required force.

The process of this invention is most clearly described by a series ofillustrations, FIGS. 1-9, schematically showing the functioning of anapparatus for mechanically producing articles according to the process.

A spherical cavity for forming a solid spherical article is defined by apair of hemispherically shaped molding dies 10 and 11, respectivelycontained in a fixed die block 12 and a movable die block 13. Thespherical cavity formed by the two sections when joined is most clearlyillustrated in FIG. 5. An ejector rod 14 is shown disposed between theseparated sections of the mold in FIG. 1, and its function will besubsequently described. The ejector rod is normally withdrawn from thearea of the cavity.

An elongated rod 15 of malleable metal such as aluminum, copper, orlead, for example, having a uniform crosssection along its length istransported from a source (not shown) down a passageway to the fixed dieblock 12, and a predetermined length 18 thereof is severed from rod 15by cutting die 16 as it passes downward into chamber 17 in the dieblock. The required length of material is readily determined knowing itscross section dimension and the volume of the cavity to be filled. Thelength 18 of the rod material is conveyed to injection chamber 19 by thecutting die 16 until it is firmly seated in the injection chamber, asmost clearly illustrated in FIG. 3. The cutting die 16 is then drawnback up cham ber 17 and the length of material 18 is injected along theinjection chamber 19 into the cavity by plunger 20. Concurrentlytherewith, the movable die block 13 moves rightward toward the fixed dieblock during this injection phase, as most clearly illustrated in FIG.4. In FIG. 5 it can be seen that at the time the leftmost end of the rodmaterial 18 impacts the cavity-defining wall surface of the hemisphericdie section 11, die blocks 12 and 13 are juxtapositioned along theirseparation line 21 so as to completely close the mold. The two diesections of the mold are brought together concurrently while thematerial is being injected so that air in the cavity which is displacedby the injected material may be exhausted. At the instant of initialimpact of the material against the inner wall of die 11 there may besome small separation of the two die blocks to facilitate exhaustion ofentrapped air. However, by the time the material reaches the separationline while conforming to the contour of the cavity, the two die blocksare completely closed together so that no flashing occurs along theseparation line. It has been found that there are suflicient minuteopenings, such as where the injection chamber 19 joins die 10, throughwhich air can escape while the material completely fills the cavity. Theforce applied to the length of malleable metal at the time of impact andcontinuously for a period of time thereafter by plunger 20, effectivelycauses the metal to flow away from the point of impact to completelyfill the cavity in a homogeneous mass shaped to the contour of thecavity as indicated at 22.

The amount of applied force is dependent upon various factors, foremostof which is the malleability of the injected material. Related to themalleability is a phenomenon which will be referred to as cold flow.Obviously, the more malleable solid metals, such as lead and leadalloys, require less amount of compression force than metals ofrelatively lower malleability. Less malleable metals, such as copper andaluminum based metals, may have to be injected at a high velocity toimpact the wall of the cavity with an explosive-like force to initiatecold flow of the metal. A constant force applied thereafter will causethe metal to continue the cold flow and form to the cavity in ahomogeneous mass. Lead and lead alloys will flow with less pressureapplied at a more gradual rate.

It has also been found that the force and velocity of injection dependsupon the size and shape of the article to be formed. For example,greater force is required to form an article having sharp indentationsor protrusions than one having an uninterrupted outer surface, such as asphere. Although some orders of magnitude are recited hereinafter forillustrative purposes, in general these must be determined empiricallyfor each situation.

To remove the formed article 22, the mold cavity is opened bywithdrawing the movable die block 13 in a leftward direction to separatethe two die sections, and 11. As illustrated in FIG. 7, the formedarticle has a tendency to adhere to the surface of the cavity as aresult of the forceful injection of the material. Further leftwardmotion of plunger pushes the formed article away fr m the inner surfaceof die section 10 as shown in FIG. 8. Since the formed article may alsohave a tendency to adhere to the end of plunger 26, it is freed by beingstruck by ejector .pin 14 which can be brought into position after themold has been opened.

FIGS. 1017 show various views of an embodiment of an apparatusconstructed to produce solid sphericalshaped articles of lead or leadalloy at a rapid rate of production by the cold-die casting method ofthis invention. Identical parts shown in the various figures areidentified with identical item numbers.

A mean housing generally designated 24, has a base 25, a top 26 andadditional strengthening structure, not separately identified, which maybe considered generally as wall supports between the base and top. Thehousing is preferably constructed as a unitary structure either bycasting it as a single item or by welding or bolting together thevarious sections.

It is intended that FIG. 10 convey the concept of the massiveness andstrength of the main housing 24 and the other component parts which arenecessitated by the relatively large motivating forces and the speed ofthe machine when in operation. The main drive shaft 27 is journaled inthe housing and is rotationally driven by a motivating power source, notshown, which is preferably located rearward of the main housing.Externallytoothed spur gear 28 which is axially attached to shaft 27meshes with spur gear 29 to drive spur gear 30 and drum or cylinder cam31 coaxially attached, along with gear 29, to shaft 32, journaled in themain housing. Spur gear 33 is meshed with idler gear 34 diametricallyopposite gear 36 and is axially attached to shaft 35, suitably journaledin the housing.

Attached to shaft 27 at its forward extremity is cam 36 linked toimpeller arm 37 by cam follower rollers 38 and 39 which are positivelydriven by engagement with the inner and outer surfaces respectively ofcam 36. Extending leftward from its attachment to impeller arm 37 isinjector plunger 40. As cam 36 rotates it causes impeller arm 37 toreciprocally slide leftward and rightward along guide ways in theforwardly located wall support 41 of main housing 24. Correspondingly,plunger 40 injects and withdraws along cylindrical injection chamber 42which opens into the cavity at the die section 43 contained in fixed dieblock 44. The portion of the profile of cam 36 which drives injectorplunger towards the cavity during injection is designed to provide ageneral constant acceleration-constant deceleration motion to theplunger and the lead material being injected. The maximum displacementeffected by the cam profile during injection is such that continuouspressure is applied to the injected metal so that it flows to fill thecavity. Shortly after the maximum displacement position of the contourof cam 36 is a small hump, 23 (FIG. 11) which, as will be laterdescribed in greater detail, aids ejection of the formed article. Theremainder of the cam profile controls withdrawal of the plunger andincludes a dwell section.

As most clearly shown in FIG. 16, a feed passage 45 in the fixed dieblock 44 runs parallel to the injection chamber 42 to receive the rod 46of malleable metal to be formed. Chamber 47 provides a passageway forcutting die 48 to carry the severed section of the rod into injectionchamber 42. The cutting end 49 of die 48 is curved in correspondencewith a portion of the peripheral surface of the rod 46 to ensure thatthe severed section is properly seated in the injection chamber. Plunger46 is constructed from extremely hard tool steel with a high resistanceto fatigue. Its surface is polished to a fine finish so that even thoughit sits snugly in the injection chamber it can be driven along thechamber with sufficient acceleration to impart the required force to thematerial being injected. The end of the plunger which is in contact withthe material during injection has a curvature since it closes theopening through which the material is injected into the cavity andtherefore forms part of the cavity wall. Injection chamber 40 is formedto a highly polished finish in a different material such as tungstencarbide.

Attached to the front end of shaft 35 is another cam 53. Impeller arm 51is linked to cam by cam follower rollers 52 and 53 respectively engagedwith the inner and outer surfaces of cam Stl. Attached to impeller arm51 is movable die block 54 containing the other hemispheric section 55of the mold. As cam 53 rotates, it causes impeller arm 51 to cyclicallyslide rightward and leftward, respectively corresponding to theinjection and withdrawal phases of the cyclical operation, alongguideways 56 and 57 (FIGS. 13 and 14) in support members of the mainhousing 24. The cam profiles and gear driving arrangements are such thatplunger 40 and movable die block 54 operate substantially concurrentlyin the respective injection and withdrawal phases.

Cam follower 58 rides in the cam channel 59 on drum cam 31 and isattached to stop member 60 mounted to a pair of elongated shafts 61 and62 which slidably pass through their respective cylindrical bores 63 and64 in the main housing 24, as most clearly shown in FIG. 15. As drum cam31 is rotationally driven by shaft 32, the cam follower 58 is positivelydriven to impart linear reciprocating forward and backward motion toshafts 61 and 62 along their respective bores. In general, the profileof cam channel 59 is such that when injector plunger 40 is positioned inthe vicinity of its rightmost or furthest withdrawn position by cam 36,shafts 61 and 62 are being driven rearwardly and as movable die block 54is being driven leftward during the withdrawal phase by cam 50, shafts61 and 62 are being driven in the forward direction. Attached to thefront end of shafts 61 and 62 is block 65 containing cutting die 48 andstop members 66 and 67. Extending forward from its attachment to stopmember 60 parallel to rods 61 and 62 is ejector pin 68. When cutting die48 is being driven rearward to sever the rod of malleable metal andposition the severed piece in the injection chamber 42 in preparationfor the injection phase, ejector pin 68 is being removed from betweenthe die blocks. During the withdrawal phase, ejector pin 68 is drivenforward to strike the formed article and free it from the end of plunger40.

Each cycle of operation of the machine basically comprises two phases,an injection phase and a withdrawal phase. However, to achieve maximumproduction rates there is some overlap of these two basic phases. Forexample, machine operations which prepare the malleable metal forinjection are considered to be part of the injection phase.Additionally, as will be subsequently 'described in greater detail, theinjection plunger is used to aid in ejecting the article so even thoughejection is part of the withdrawal phase, the plunger may not yet bewithdrawn.

The operation of the machine can best be described by considering atypical operation to produce lead balls having a diameter of .250 inch.Each of the hemispheric sections 43 and 55 of the spherical cavity aresuitably formed to the required corresponding dimensions in theirrespective die blocks 44 and 54 and an elongated solid rod of leadhaving a diameter of .100 inch is positioned in feed chamber 45 with asuitable length opposite the cutting face of cutting die 48. It will beassumed that the machine has been operating normally at its cyclicalrate with considered to be the start of the injection phase which issubstantially as illustrated in FIG. 11. The operative portion of theprofile of cam 36 is such that plunger 40 will either be dwelling in itsfurthest withdrawn position or will be withdrawing so that it does notblock the opening where chamber 47 joins injection chamber 42.Similarly, the operative section of the profile of cam 50 will be suchthat the movable die block 54 will be dwelling in its furthest withdrawnposition or may be starting to close toward the fixed die block 44 at arelatively slow rate. As drum cam 31 is rotationally driven by the maindrive shaft 27 through the gear train comprising spur gears 28 and 29,cam follower 58 in following track 59 causes block 65 to move rearwardby its connection thereto via stop member 60 and shafts 61 and 62 (FIG.15). Cutting die 48 is thereby driven down chamber 47 toward theinjection chamber 42 and cuts off a one inch length of the rod of leadand delivers it to the injection chamber. Concurrently, of course,ejector pin 68 is being moved rearward away from the general vicinity ofthe mold. As the severed length of the rod is seated in the injectionchamber the now operative portion of the profile of cam 36, which isbrought into play by the rotation of the main drive shaft 27, initiatesinjection travel of plunger 40 via cam followers38 and 39 and impellerarm 37, such that the leading edge of the injection plunger is incontact with the piece of lead in the injection chamber. At the sametime, cam 50 has been rotated by main drive shaft 27 via the gear traincomprising gears 28,

29, 30, 34 and 33 so that the operative portion of its profile is movingthe movable die block 54 via cam followers 52 and 53 and impeller arm 51toward the fixed die block 44 to close the spherical cavity of the mold.As the cutting die 48 is moved forward away from injection chamber 42while movable die block 54 has been positioned to almost completelyclose the cavity except for a small gap along the separation linebetween the two sections of the cavity, the injection-controllingportion of the profile of cam 36 becomes operative to inject the metalinto the cavity 43, where it joins injection chamber 42, with therequired force. With the cavity completely closed, the leading edge ofthe injected material impacts the smooth surfaced wall of cavity section55 and is subjected to pressure ranging in the order of 30,000 to 100,-000 p.s.i. and is compressed to flow as a homogeneous mass completelyfilling the now closed cavity and shaped to conform with the cavitycontour. It should be noted that 'by accurate machining of the profileof cam 50, the movable die block 54 can be gapped from the fixed dieblock 44 for a suificient length of time to allow maximum escape ofentrapped air. The cavity is completely closed by the controlling actionof cam 50 when the compressed material reaches that part of the cavitywall containing the separation line between the two sections of a mold.This can be considered to be the termination of the injection phase ofthe cycle of operation.

The withdrawal phase is initiated by that portion of the profile of cam50 which now becomes operative to open the cavity by separating themovable die block 54 from juxtaposition with the fixed die block 44.

Correspondingly, the ejector pin 68 is brought forward into the area ofthe cavity under control of the drum cam 31. This forward movement ofthe ejector pin, which is considered to be part of the withdrawal phase,is actually initiated during the injection phase since it is drivenforward at the same time that the cutting die 48 is being moved awayfrom the injection chamber. This is a part of the operation whichillustrates overlap between the two phases of the cycle of operation.While the cavity is being opened and ejector pin 68 is being movedforward, the operational portion 23 of the profile of cam 36 directs theinjection plunger 40 further leftward so that it presses against theformed spherical lead ball to separate it from the wall of thehemispheric section 43 of the cavity. As the ball is pushed away fromthe wall of the cavity, the front end of ejector pin 68 strikes it todislodge it from the plunger 40 so that it falls free into a receivingchamber, not shown. The forceful ejection action by plunger 40 andejector pin 68 is required since the force with which the material iscompressed in the cavity is such that the formed article has a tendencyto adhere to the wall of the cavity and the contacting end of theplunger.

The force applied to the movable die block 54 to open the cavity must besufiicient to overcome this adhering force.

There is a possibility that the ball will adhere to the wall of diesection 55 when the movable die block 54 is separated from the fixed dieblock. To compensate for this possibility, a holding pin which is springbiased and extends through the movable die block into communication withthe hemispheric section 55 is incorporated to apply sufficient force onthe lead ball to separate from the cavity Wall in the movable die block.When the lead ball has been ejected, the withdrawal phase is consideredterminated and a new injection phase initiates another cycle. Overlap ofthe phases is again illustrated since the plunger "40 is being withdrawnalong injection chamber 42 by the operative portion of cam 36 after theinjection phase I begins.

Although the description of the process and apparatus for cold diecasting malleable metals has been directed toward the formation ofspherical shaped object, it is evident that articles of various precisesizes and shapes can be fabricated according to the teachings of thisinvention. For example, a more complex shaped article, shown in sideandfront views respectively in FIGS. 18 and 19, comprises a pair ofhemispheric jaws 69 and 70 hinged together at 72 to form a gap 71 whenin the open position. A pair of tongues 73 and 74 extend downward belowthe hinge. The jaw faces are indented to provide more effective clampingaction when the jaws are closed together. This is indicated by thedashed lines in FIGS. 18 and 19.

This article is formed from lead and the depth of the cut forming gap 71is critical so that the jaws may be manually opened and closed manytimes without use of a special tool while the hinge retains itsstrength. A quantity of articles of this configuration have beenproduced according to the method of this invention by an apparatussubstantially similar to that described herein at a production rate inthe order of 200 per minute. Suitable lengths of a solid lead rod toprovide the required volume of material were injected with sufficientforce to develop pressures in the range previously recited, at theproduction rate into a cavity defined by a pair of separable sections,each section having an internal cavity wall contour conforming to thedesired configurations of the corresponding part of the article. The diesection in the movable die block had a protrusion corresponding to thedesired gap between the jaws and the end of the ejection plunger wastapered to the configuration of the V-shaped slot between the tonguemembers 73 and 74 since the end of the plunger forms part of the closedcavity, as previously described.

It should be evident that the required compression forces depend uponthe type of material being injected and the shape and size of thearticle being formed. This further has a bearing on the selection ofappropriate length and diameter of the injected rod of material. Ingeneral, there may be a range of choices and a suitable choice can bedetermined empirically. Obviously, the more malleable the metal, forexample, lead as compared to copper, the wider is the range ofselection.

Selection of metals which can be formed according to this inventiveprocess is dependent upon various characteristics of the metal, such asits hardness, modulus of elasticity, crystalline structure, etc. Withoutattempting to make a rigorous analysis of the behavior of the metal whensubjected to pressures in the manner taught by the invention, it istheorized that the above characteristics (and others) determine themetals susceptibility to flow empirically.

We claim:

1. A method for forming an article from malleable metal by die casting,comprising the steps of:

(a) forming a slug by cutting a length from the end of an elongated rodof malleable metal having a longitudinal uniform solid cross section,the volume of said slug being substantially equal to the volume of thearticle to be formed;

(b) feeding the slug into an injection chamber through an openinglocated away from the die cavity;

(c) injecting said slug into the cavity of a separable sectioned moldfrom the injection chamber through an opening in a wall of the mold onlyafter the cavity has been substantially closed with the injection forcebeing such to compress the metal into a homogeneous mass conforming tothe cavity contour by impact with the cavity-defining surface of themold.

2. A machine for cold die casting malleable metals, comprising: a fixeddie block and a movable die block each containing a section of a moldcavity; means for reciprocatingly driving said movable die block towardand away from said fixed die block to correspondingly close and opensaid cavity; means for feeding a solid piece of malleable metal into aninjection chamber at a location away from the die block opening, plungermeans for injecting said solid piece of malleable metal into the cavityfrom the injection chamber through an opening in the wall of the fixeddie block only after the cavity is substantially closed to impact thecavity wall on the movable die block within a compression force causingthe metal to flow and form to the cavity in a homogeneous mass; saidplunger advancing further into the cavity after the injection stroke 3while said die blocks are separating to push the formed piece away fromthe wall of the fixed die block.

3. The machine as described in claim 2 further including: means forreciprocatingly driving said plunger between said feeding location andsaid cavity for injecting the fed metal from the feeding location intothe cavity with compression force to form it and for pushing the formedpiece away from the wall of the fixed die block when the die blocks areseparating.

4. A machine for cold die casting malleable metals comprising: a fixeddie block and a movable die block each containing a section of a moldcavity; means for reciprocatingly driving said movable die block towardand away from said fixed die block to correspondingly close and opensaid cavity; an injection chamber opening into the cavity sectionthrough the wall in said fixed die block; a plunger slidingly engaged insaid injection chamber; means for reciprocatingly driving the plunger insaid injection chamber toward and away from said cavity for providingcompression force on the metal as it impacts the cavity wall on themovable die block when it is injected into the cavity after the cavityis substantially closed; feed chamber means for feeding an elongatedsolid rod of malleable metal; and a cutting tool for cutting off aprescribed length of the rod at one end thereof to form a slug and forfeeding the slug through the feed chamber into said injection chamber,the cutting edge of said cutting tool forming part of the wall of theinjection chamber when it is positioning the slug therein.

References Cited UNITED STATES PATENTS 1,613,595 1/1927 Abel 723532,687,660 8/1954 Friedman 72-346 2,800,814 7/1957 Lewis 7236O 3,036,3675/1962 Ricks 72356 CHARLES W. LANHAM, Primary Examiner.

L. A. LARSON, Assistant Examiner.

2. A MACHINE FOR COLD AIR CASTING MALLEABLE METALS, COMPRISING: A FIXEDDIE BLOCK AND A MOVABLE DIE BLOCK EACH CONTAINING A SECTION OF A MOLDCAVITY; MEANS FOR RECIPROCATINGLY DRIVING SAID MOVABLE DIE BLOCK TOWARDAND AWAY FROM SAID FIXED DIE BLOCK TO CORRESPONDINGLY CLOSE AND OPENSAID CAVITY; MEANS FOR FEEDING A SOLID PIECE OF MALLEABLE METAL INTO ANINJECTION CHAMBER AT A LOCATION AWAY FROM THE DIE BLOCK OPENING, PLUNGERMEANS FOR INJECTING SAID SOLID PIECE OF MALLEABLE METAL INTO THE CAVITYFROM THE INJECTION CHAMBER THROUGH AN OPENING IN THE WALL OF THE FIXEDDIE BLOCK ONLY AFTER THE CAVITY IS SUBSTANTIALLY CLOSED TO IMPACT THECAVITY WALL ON THE MOVABLE DIE BLOCK WITHIN A COMPRESSION FORCE CAUSINGTHE METAL TO FLOW AND FORM TO THE CAVITY IN A HOMOGENEOUS MASS; SAIDPLUNGER ADVANCING FURTHER INTO THE CAVITY AFTER THE INJECTION STROKEWHILE SAID DIE BLOCKS ARE SEPARATING TO PUSH THE FORMED PIECE AWAY FROMTHE WALL OF THE FIXED DIE BLOCK.